git.sesse.net Git - remoteglot/blob - www/serve-analysis.js

   1 // node.js version of analysis.pl; hopefully scales a bit better
   2 // for this specific kind of task.
   3
   4 // Modules.
   5 var http = require('http');
   6 var fs = require('fs');
   7 var url = require('url');
   8 var querystring = require('querystring');
   9 var path = require('path');
  10 var zlib = require('zlib');
  11
  12 // Constants.
  13 var json_filename = '/srv/analysis.sesse.net/www/analysis.json';
  14
  15 // The current contents of the file to hand out, and its last modified time.
  16 var json_contents = undefined;
  17 var json_contents_gz = undefined;
  18 var json_last_modified = undefined;
  19
  20 // The list of clients that are waiting for new data to show up,
  21 // and their associated timers. Uniquely keyed by request_id
  22 // so that we can take them out of the queue if they time out.
  23 var sleeping_clients = {};
  24 var request_id = 0;
  25
  26 // List of when clients were last seen, keyed by their unique ID.
  27 // Used to show a viewer count to the user.
  28 var last_seen_clients = {};
  29
  30 var reread_file = function(event, filename) {
  31         if (filename != path.basename(json_filename)) {
  32                 return;
  33         }
  34         console.log("Rereading " + json_filename);
  35         fs.open(json_filename, 'r+', function(err, fd) {
  36                 if (err) throw err;
  37                 fs.fstat(fd, function(err, st) {
  38                         if (err) throw err;
  39                         var buffer = new Buffer(1048576);
  40                         fs.read(fd, buffer, 0, 1048576, 0, function(err, bytesRead, buffer) {
  41                                 if (err) throw err;
  42                                 fs.close(fd, function() {
  43                                         var new_json_contents = buffer.toString('utf8', 0, bytesRead);
  44                                         zlib.gzip(new_json_contents, function(err, buffer) {
  45                                                 if (err) throw err;
  46                                                 json_contents = new_json_contents;
  47                                                 json_contents_gz = buffer;
  48                                                 json_last_modified = st.mtime.getTime();
  49                                                 possibly_wakeup_clients();
  50                                         });
  51                                 });
  52                         });
  53                 });
  54         });
  55 }
  56 var possibly_wakeup_clients = function() {
  57         for (var i in sleeping_clients) {
  58                 clearTimeout(sleeping_clients[i].timer);
  59                 send_json(sleeping_clients[i].response, sleeping_clients[i].accept_gzip);
  60         }
  61         sleeping_clients = {};
  62 }
  63 var send_404 = function(response) {
  64         response.writeHead(404, {
  65                 'Content-Type': 'text/plain',
  66         });
  67         response.write('Something went wrong. Sorry.');
  68         response.end();
  69 }
  70 var send_json = function(response, accept_gzip) {
  71         var headers = {
  72                 'Content-Type': 'text/json',
  73                 'X-Remoteglot-Last-Modified': json_last_modified,
  74                 'X-Remoteglot-Num-Viewers': count_viewers(),
  75                 'Access-Control-Allow-Origin': 'http://analysis.sesse.net',
  76                 'Access-Control-Expose-Headers': 'X-Remoteglot-Last-Modified, X-Remoteglot-Num-Viewers',
  77                 'Expires': 'Mon, 01 Jan 1970 00:00:00 UTC',
  78         };
  79
  80         if (accept_gzip) {
  81                 headers['Content-Encoding'] = 'gzip';
  82                 response.writeHead(200, headers);
  83                 response.write(json_contents_gz);
  84         } else {
  85                 response.writeHead(200, headers);
  86                 response.write(json_contents);
  87         }
  88         response.end();
  89 }
  90 var timeout_client = function(client) {
  91         send_json(client.response, client.accept_gzip);
  92         delete sleeping_clients[client.request_id];
  93 }
  94 var count_viewers = function() {
  95         var now = (new Date).getTime();
  96
  97         // Go through and remove old viewers, and count them at the same time.
  98         var new_last_seen_clients = {};
  99         var num_viewers = 0;
 100         for (var unique in last_seen_clients) {
 101                 if (now - last_seen_clients[unique] < 60000) {
 102                         ++num_viewers;
 103                         new_last_seen_clients[unique] = last_seen_clients[unique];
 104                 }
 105         }
 106         last_seen_clients = new_last_seen_clients;
 107         return num_viewers;
 108 }
 109
 110 // Set up a watcher to catch changes to the file, then do an initial read
 111 // to make sure we have a copy.
 112 fs.watch(path.dirname(json_filename), reread_file);
 113 reread_file(null, path.basename(json_filename));
 114
 115 http.createServer(function(request, response) {
 116         var u = url.parse(request.url, true);
 117         var ims = (u.query)['ims'];
 118         var unique = (u.query)['unique'];
 119
 120         console.log((new Date).getTime()*1e-3 + " " + request.url);
 121
 122         if (u.pathname !== '/analysis.pl') {
 123                 // This is not the request you are looking for.
 124                 send_404(response);
 125                 return;
 126         }
 127
 128         if (unique) {
 129                 last_seen_clients[unique] = (new Date).getTime();
 130         }
 131
 132         var accept_encoding = request.headers['accept-encoding'];
 133         var accept_gzip;
 134         if (accept_encoding !== undefined && accept_encoding.match(/\bgzip\b/)) {
 135                 accept_gzip = true;
 136         } else {
 137                 accept_gzip = false;
 138         }
 139
 140         // If we already have something newer than what the user has,
 141         // just send it out and be done with it.
 142         if (json_last_modified !== undefined && (!ims || json_last_modified > ims)) {
 143                 send_json(response, accept_gzip);
 144                 return;
 145         }
 146
 147         // OK, so we need to hang until we have something newer.
 148         // Put the user on the wait list; if we don't get anything
 149         // in 30 seconds, though, we'll send something anyway.
 150         var client = {};
 151         client.response = response;
 152         client.timer = setTimeout(function() { timeout_client(client); }, 30000);
 153         client.request_id = request_id;
 154         client.accept_gzip = accept_gzip;
 155         sleeping_clients[request_id++] = client;
 156 }).listen(5000);